Seat occupant detection is frequently used in connection with air bags and other pyrotechnically deployed restraints as a means of determining if the restraints should be deployed in the event of sufficiently severe crash. A significant challenge arises from the desire to minimize the cost-impact of occupant detection while retaining the ability to distinguish between a normally seated occupant and an infant or child seat that is cinched down against the seat with a seat belt. Unfortunately, the most cost effective sensing approaches such as seated weight sensing cannot reliably discriminate between these two types of occupants because they have similar apparent weight. While it is certainly possible to equip the vehicle with two or more different types of sensors and discriminate between occupant types based on all of the sensor data, the cost of doing so is usually too high. Accordingly, what is needed is a cost-effective occupant detection sensor that can reliably distinguish between a normally seated occupant and a cinched down infant or child seat.